Mechanical coolant pumps are described in DE 10 2008 027 157 A1. These pumps comprise a pump rotor wheel driven by the engine and a static blade holding ring with numerous pivotable pump stator blades. The cool is fully controllable so that the coolant flow in the coolant circuit of a combustion engine can be adapted to the engine's need. The control of such a pump is realized by actuation of all pivotable pump stator blades, which is typically performed mechanically or electronically. The actuation of all pump stator blades requires a high actuation power, however, due to the high hydraulic and mechanical forces which act on each blade. As a result, the actuator which must be able to provide the maximum actuation power must be relatively large and energy consuming.